In this work, we present two novel detection methods, utilizing the Fourier domain representation of an image or its feature maps, to decide whether it is a benign or an adversarial image. Employing the Fourier spectrum to extract features imperceptible to human eyes has shown to be successful before, for example, to detect Deepfakes [1]}, [2]}. As the adversarial perturbations depend on and interact with the image content, they are usually hard to grasp at a pixel level. Yet, we argue that a spatial-invariant representation such as the Fourier spectrum facilitates to discern of such subtle but systematic modifications.
